Methods of fabricating polycrystalline diamond elements and compacts using sp2-carbon-containing particles

ABSTRACT

Methods of fabricating polycrystalline diamond elements and compacts using sp 2 -carbon-containing particles are disclosed. In an embodiment, a method of fabricating a polycrystalline diamond element includes mixing a plurality of sp 2 -carbon-containing particles and a plurality of diamond particles to form a mixture. An amount of the plurality of sp 2 -carbon-containing particles present in the mixture is effective to increase a thermal stability of the polycrystalline diamond element formed at least partially from the mixture. The method further includes sintering the mixture in the presence of a catalyst material to form the polycrystalline diamond element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/394,594filed on 27 Feb. 2009, which is a continuation of application Ser. No.11/496,905 filed on 31 Jul. 2006, now U.S. Pat. No. 7,516,804. Each ofthe foregoing applications is incorporated, in its entirety, by thisreference.

TECHNICAL FIELD

The present invention relates to superabrasive materials, apparatuses,and methods of manufacturing same, such as polycrystalline diamond (PCD)elements and applications utilizing such elements in drilling tools(e.g., inserts, cutting elements, gage trimmers, etc.), machiningequipment, bearing apparatuses, wire drawing machinery, and otherapparatuses.

BACKGROUND

Polycrystalline diamond compacts (“PDCs”), such as cutting elements usedin rock bits or other cutting tools, typically include a cementedtungsten carbide substrate having a layer of superabrasive PCD (alsocommonly referred to as a diamond table) bonded to a surface of thesubstrate using an ultra-high pressure, ultra-high temperature (“HPHT”)process. Sometimes, the substrate may be brazed or otherwise joined toan attachment member such as a stud or to a cylindrical backing, ifdesired. A stud carrying a PDC may be used as a subterranean cuttingelement when mounted to a drill bit by press-fitting, brazing, orotherwise locking the stud into a receptacle formed in the subterraneandrill bit or by brazing the cutting element directly into a preformedpocket, socket, or other receptacle formed in the subterranean drillbit. For example, cutter pockets may be formed in the face of a bitformed of cemented tungsten carbide. Generally, a rotary drill bit mayinclude a plurality of PCD superabrasive cutting elements affixed to thedrill bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container or cartridge with a volume of diamondcrystals or particles positioned on a surface of the substrate. A numberof such cartridges may be typically loaded into an ultra-high pressurepress. The substrates and volume of diamond particles are then processedunder HPHT conditions in the presence of a catalyst material that causesthe diamond grains to form and to bond to one another to form a matrixof bonded diamond grains defining a diamond table. The catalyst materialis often a solvent catalyst, such as cobalt, nickel, or iron that isused for facilitating the intergrowth of the diamond grains. In oneprocess, a constituent of the substrate, such as cobalt from acobalt-cemented tungsten carbide substrate, becomes liquid and sweepsfrom the region adjacent to the volume of diamond grains and intointerstitial regions between the diamond grains during the HPHT process.The cobalt acts as a catalyst to facilitate the intergrowth processbetween the diamond grains, which results in bonds between adjacentdiamond grains. Often, a solvent catalyst may be mixed with the diamondparticles prior to subjecting the diamond particles and the substrate tothe HPHT process.

As known in the art, the solvent catalyst may dissolve carbon from thediamond particles or portions of the diamond particles that graphitizedue to the high temperatures being used. The solubility of the stablediamond phase in the solvent catalyst is lower than that of themetastable graphite under HPHT conditions. As a result of thissolubility difference, the undersaturated graphite tends to dissolveinto solvent catalyst and the supersaturated diamond tends to depositonto existing diamond grains to form diamond-to-diamond bonds.Accordingly, diamond grains become mutually bonded to form a matrix ofPCD with interstitial regions between the bonded diamond grains beingoccupied by the solvent catalyst.

However, the presence of the solvent catalyst in the diamond table canlead to a diamond table that may be thermally damaged at elevatedtemperatures. For example, the difference in thermal expansioncoefficient between the diamond grains and the solvent catalyst isbelieved to lead to chipping or cracking in the PDC during drilling orcutting operations, which consequently can degrade the mechanicalproperties of the PDC or cause failure. Additionally, it is believedthat some of the diamond grains can undergo a chemical breakdown orback-conversion with the solvent catalyst. Of course, at extremely hightemperatures, diamond may transform to carbon monoxide, carbon dioxide,graphite, or combinations thereof degrading the mechanical properties ofthe PDC.

Therefore, there is a still a need for a superabrasive material (e.g.,PCD) exhibiting superior mechanical and/or thermal properties (e.g., anincreased amount of bonding between superabrasive grains).

SUMMARY

The present invention is directed to superabrasive materials andelements, such as PCD elements, methods of fabricating superabrasiveelements, and applications utilizing such elements. One aspect of thepresent invention is directed to a superabrasive element comprising amass of polycrystalline diamond including ultra-dispersed diamond grainstructures present in an amount greater than zero weight percent andless than about 75 weight percent of the mass of polycrystallinediamond. In one embodiment, the ultra-dispersed diamond grain structuresmay be present in an amount greater than zero weight percent and lessthan about 45 weight percent of the mass of polycrystalline diamond.

An additional aspect of the present invention is directed to a method offabricating a superabrasive element. A mixture including a first type ofsuperabrasive particles comprising ultra-dispersed diamond particles anda second type of superabrasive particles is provided. Theultra-dispersed diamond particles are present in an amount greater thanzero weight percent and less than about 75 weight percent of themixture. The mixture is sintered by application of heat and pressure inan amount sufficient to form the superhard element. In one embodiment,the ultra-dispersed diamond particles may be present in an amountgreater than zero weight percent and less than about 45 weight percentof the mixture.

Another aspect of the present invention is directed to a PDC. The PDCincludes a substrate and a superabrasive table bonded to the substrate.The superabrasive table includes a mass of polycrystalline diamondcomprising ultra-dispersed diamond grain structures present in an amountgreater than zero weight percent and less than about 75 weight percentof the mass of polycrystalline diamond. In one embodiment, theultra-dispersed diamond grain structures may be present in an amountgreater than zero weight percent and less than about 45 weight percentof the mass of polycrystalline diamond.

A further aspect of the present invention is directed to a drill bit.The drill bit includes a bit body adapted to engage a subterraneanformation during drilling. At least one superabrasive cutting element isaffixed to the bit body. The at least one superabrasive cutting elementincludes a mass of polycrystalline diamond comprising ultra-disperseddiamond grain structures present in an amount greater than zero weightpercent and less than about 75 weight percent of the mass ofpolycrystalline diamond. In one embodiment, the ultra-dispersed diamondgrain structures may be present in an amount greater than zero weightpercent and less than about 45 weight percent of the mass ofpolycrystalline diamond.

Yet a further aspect of the present invention is directed to variousdifferent apparatuses, such as drilling tools, machining equipment,bearing apparatuses, wire drawing machinery, and other apparatuses thatemploy the inventive superabrasive elements disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial, schematic microstructural representation of asintered superabrasive element in accordance with one embodiment of thepresent invention.

FIG. 2 is a partial, schematic microstructural representation of amixture of a first type of superabrasive particles formed of relativelycoarse superabrasive particles and a second type of superabrasiveparticles formed of ultra-dispersed diamond particles that are used tofabricate the superabrasive element of FIG. 1 in accordance with oneembodiment of a method of the present invention.

FIG. 3 is a schematic diagram illustrating a method for fabricating asuperabrasive element on a substrate in accordance with one embodimentof the present invention.

FIG. 4 is an isometric view of one embodiment of a rotary drill bitincluding at least one cutting element comprising a superabrasiveelement fabricated and structured in accordance with embodiments of thepresent invention; and

FIG. 5 shows a top elevation view of the rotary drill bit of FIG. 4.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The present invention is directed to superabrasive (e.g., PCD) elements,methods of fabricating such elements, and applications utilizing suchelements. The superabrasive elements disclosed herein may be used in avariety of applications such as drilling tools (e.g., compacts, inserts,cutting elements, gage trimmers, etc.), machining equipment, bearingapparatuses, wire drawing machinery, and other apparatuses. The presentinvention relates generally to structures comprising at least onesuperabrasive material (e.g., diamond, boron nitride, silicon carbide,mixtures of the foregoing, or any material exhibiting a hardnessexceeding a hardness of tungsten carbide) and methods of manufacturingsuch structures. More particularly, the present invention relates to asintered superabrasive mass or volume and methods of manufacturing sucha material. As used herein, “superabrasive,” means a material exhibitinga hardness exceeding a hardness of tungsten carbide. For example,ultra-dispersed diamond particles may be employed for enhancingpolycrystalline diamond. In another example, ultra-dispersed diamondparticles may be employed for enhancing a superabrasive material asdisclosed in U.S. Pat. No. 7,060,641, the disclosure of which isincorporated herein, in its entirety, by this reference.

Many specific details of certain embodiments of the present inventionare set forth in the following description and in FIGS. 1 through 5 inorder to provide a thorough understanding of such embodiments. While theembodiments described below reference PCD or PDC material, one skilledin the art will understand that the present invention may haveadditional embodiments, or that the present invention may be practicedwithout several of the details described in the following description.In the figures and description below, like or similar reference numeralsare used to represent like or similar elements.

Various embodiments of the present invention are directed to sinteredsuperabrasive elements that include a mass of sintered superabrasiveparticles comprising ultra-dispersed diamond grain structures present inan amount greater than zero weight percent and less than about 75 weightpercent of the mass of sintered superabrasive particles. As used herein,“ultra-dispersed diamond particles,” also commonly referred to in theart as nanocrystalline diamond particles, means particles eachcomprising a polycrystalline diamond core surrounded by a metastablecarbon shell. Such ultra-dispersed diamond particles may exhibit aparticle size of about 1 nm to about 50 nm and more typically, of about2 nm to about 20 nm, and agglomerates of ultra-dispersed diamondparticles may be between about 2 nm to about 200 nm. Ultra-disperseddiamond may be formed by detonating trinitrotoluene explosives in achamber and subsequent purification to extract diamond particles oragglomerates of diamond particles with the diamond particles generallycomprising a polycrystalline diamond core surrounded by a metastableshell, which includes amorphous carbon, carbon onion (i.e., closed shellsp² nanocarbons), or both. Ultra-dispersed diamond particles arecommercially available from ALIT Inc. of Kiev, Ukraine. The presentinvention contemplates that as a result of, at least in part, utilizingultra-dispersed diamond particles in the fabrication process for forminga superabrasive material, the sintered superabrasive material (e.g.,PCD) may exhibit enhanced bonding between superabrasive (e.g., diamond)grains and, consequently, increased density, thermal stability, and/orother enhanced physical and/or mechanical properties.

In general, as used herein, the term “particle” or variants thereof,refers to the powder employed prior to sintering a superabrasivematerial. Further, the term “grain” or the phrase “grain structures,” orvariants thereof, refers to discernable superabrasive regions subsequentto sintering, as known and as determined in the art. The phrase“ultra-dispersed diamond grain structure,” as used herein, refers to anultra-dispersed diamond particle that has been exposed to an HPHTprocess, without regard to whether the metastable shell existssubsequent to sintering. As used herein, the phrase “HPHT process” meansto generate a pressure of at least about 40 kilobar and a temperature ofat least about 1000° C.

FIG. 1 shows a partial, schematic microstructural representation of asintered superabrasive element 2 in accordance with one embodiment ofthe present invention. The superabrasive element 2 includes coarsediamond grains 4 (represented by the large cross-hatched regions) thatare bonded to each other to define grain boundaries. The interstitialregions between adjacent coarse diamond grains 4 are occupied byrelatively fine ultra-dispersed diamond grain structures 6 that arebonded to the coarse diamond grains 4 and, depending upon the size ofthe interstitial regions, other ultra-dispersed diamond grain structures6. Although not illustrated in FIG. 1, it should be understood that theultra-dispersed diamond grain structures 6 exhibit a polycrystallinegrain structure.

The ultra-dispersed diamond grain structures 6 are present in thesuperabrasive element 2 in an amount greater than zero weight percentand less than about 75 weight percent, and in a more specific embodimentthe ultra-dispersed diamond grain structures 6 are present in an amountless than amount 45 weight percent of the superabrasive element 2. Inanother embodiment, the ultra-dispersed diamond grain structures 6 maybe present in an amount greater than zero weight percent to about 5weight percent, with the balance at least substantially being the coarsediamond grains 4. In another embodiment, the ultra-dispersed diamondgrain structures 6 may be present in an amount greater than zero weightpercent to about 4 weight percent, with the balance at leastsubstantially being the coarse diamond grains 4. In another embodiment,the ultra-dispersed diamond grain structures 6 are present in thesuperabrasive element 2 in an amount from about 0.1 weight percent toabout 3 weight percent, and more specifically in an amount from about0.1 weight percent to about 2 weight percent, with the balance at leastsubstantially being the coarse diamond grains 4. In another specificdetailed embodiment, the ultra-dispersed diamond grain structures 6 arepresent in the superabrasive element 2 in an amount from about 0.1weight percent to about 1.5 weight percent, and more specifically in anamount from about 0.1 weight percent to about 1 weight percent, with thebalance at least substantially being the coarse diamond grains 4. In yeta further detailed embodiment, the ultra-dispersed diamond grainstructures 6 are present in the superabrasive element 2 in an amountfrom about 0.1 weight percent to about 0.5 weight percent, and morespecifically in an amount from about 0.1 weight percent to about 0.25weight percent, with the balance at least substantially being the coarsediamond grains 4. In yet another detailed embodiment, theultra-dispersed diamond grain structures 6 are present in thesuperabrasive element 2 in an amount greater than zero to about 0.1weight percent with the balance at least substantially being the coarsediamond grains 4.

The coarse diamond grains 4 exhibit an average grain size (i.e.,sintered) that is greater than the average size of the ultra-disperseddiamond grain structures 6. In a more detailed embodiment, the averagegrain size of the coarse diamond grains 4 is about 0.5 μm to about 150μm and the average size of the ultra-dispersed diamond grain structures6 is about 1 nm to about 50 nm, and, more specifically, about 4 nm toabout 30 nm. In another embodiment, the coarse diamond grains 4, theultra-dispersed diamond grain structures 6, or both may exhibit abimodal or greater distribution of grain/particle sizes. It should beunderstood that any of the above ranges of various grain sizes andweight percentages for the coarse diamond grains 4 and theultra-dispersed diamond grain structures 6 may be combined.

The sintered superabrasive element 2 may exhibit a density of at leastabout 92 percent of theoretical density and may exceed at least about 98to at least about 99 percent of theoretical density. The superabrasiveelement 2 further may exhibit an increased extent of diamond-to-diamondbonding between the coarse diamond grains 4, the ultra-dispersed diamondgrain structures 6, or both. The superabrasive element 2, formed ofsubstantially only the coarse diamond grains 4 and ultra-disperseddiamond grain structures 6, may be more thermally stable than acomparative prior art PCD superabrasive element including a solventcatalyst because it does not suffer from deleterious problems commonlyexperienced when a solvent catalyst is used. However, in someembodiments, a solvent catalyst (e.g., cobalt, nickel, or iron) may alsobe employed, in at least small amounts, to promote intergrowth of thediamond grains 4 and the ultra-dispersed diamond grain structures 6 andwill be present in the interstitial regions between the coarse diamondgrains 4, the ultra-dispersed diamond grain structures 6, or both.However, such an embodiment may have a comparatively reduced thermalstability.

However, the present invention also contemplates that if thesuperabrasive element 2 is formed with both ultra-dispersed diamondparticles and a catalyst, at least a portion of the catalyst may besubsequently (i.e., after sintering) removed from the PCD element. Forexample, subsequent to sintering, a catalyst material may be at leastpartially removed (e.g., by acid-leaching, by a method as otherwiseknown in the art, or by any suitable method) from at least a portion ofa mass of polycrystalline diamond (e.g., a table formed upon asubstrate). Catalyst removal may be substantially complete to a selecteddepth from an exterior surface of the polycrystalline diamond table, ifdesired, without limitation. Thus, at least a portion of apolycrystalline diamond mass may be substantially free of a catalystemployed during sintering of the polycrystalline diamond mass. As knownin the art, at least partial catalyst removal may provide apolycrystalline diamond material with increased thermal stability, whichmay also beneficially affect the wear resistance of the polycrystallinediamond material.

The superabrasive elements disclosed herein may be fabricated inaccordance with various embodiments. For example, referring to FIG. 2,in one embodiment of a method of the present invention, a mixture 8 isformed by mixing at least one type of superabrasive (e.g., diamond)particle formed of relatively coarse superabrasive particles 10 with aselected amount of relatively fine ultra-dispersed diamond particles 12.The ultra-dispersed diamond particles 12 may be thoroughly cleaned priorto forming the mixture 8 by heating the ultra-dispersed diamondparticles 12 in a vacuum furnace for a sufficient time and temperature.The size of the coarse superabrasive particles 10 and theultra-dispersed diamond particles 12 may be selected so that most of theinterstitial regions 14 between the coarse superabrasive particles 10are occupied by one or more of the ultra-dispersed diamond particles 12.In one embodiment, the superabrasive particles 10 may comprise diamond(e.g., diamond powder or grit). As known in the art, the mixture 8 maybe placed in a pressure transmitting medium such as a refractory metalcan, graphite structure, pyrophyllite or other pressure transmittingstructures, or other containers or supporting elements. The pressuretransmitting medium, including the mixture 8, is subjected to an HPHTsintering process using an ultra-high pressure press at processconditions of, for example, a pressure of at least about 40 kilobar toat least about 70 kilobar and a temperature of at least about 1000° C.to at least about 1600° C. for a time sufficient to consolidate themixture and form a coherent mass of bonded diamond shown in FIG. 1 asthe superabrasive element 2.

During the HPHT sintering process, the coarse superabrasive particles 10of the mixture 8 that are in contact with each other will become bondedto each other. As previously discussed, most of the ultra-disperseddiamond particles 12 may occupy the interstitial regions 14 between thecoarse superabrasive particles 10. Although the physical phenomenon isnot entirely understood, it is currently believed by the inventor thatthe amorphous carbon, the carbon onion, or both in the ultra-disperseddiamond particles 12 undergo a phase transformation to diamond and bondto the coarse superabrasive particles 10. Thus, it is believed that theamorphous carbon and/or the carbon onions present in the ultra-disperseddiamond particles 12 are not stable phases at the pressures andtemperatures used in the HPHT process. Of course, as shown in FIG. 2,the interstitial regions 14 may include more than one of theultra-dispersed diamond particles 12 disposed therein. Consequently, asdepicted in FIG. 1, the interstitial regions between the coarse diamondgrains 4 may include a plurality of ultra-dispersed diamond grainstructures 6 bonded to each other. As discussed above, by forming thesuperabrasive element 2 using the coarse superabrasive particles 10 andthe metastable ultra-dispersed diamond particles 12 selected to fit intothe interstitial regions 14, the resulting sintered superabrasiveelement 2 (FIG. 1) may exhibit enhanced bonding between diamond grainsand may exhibit a density close to theoretical density, increasedthermal stability, or other enhanced physical and/or mechanicalproperties.

Prior to sintering, in one embodiment, the coarse superabrasiveparticles 10 may exhibit an average size of about 0.5 μm to about 150 μmand the ultra-dispersed diamond particles 12 may exhibit an average sizeof about 1 nm to about 50 nm, with agglomerates of the ultra-disperseddiamond particles 12 being about 2 nm to about 200 nm.

In accordance with one detailed embodiment, mixture 8 may compriseultra-dispersed diamond particles 12 in an amount greater than zeroweight percent and less than about 75 weight percent, and morespecifically in an amount less than about 45 weight percent, with thebalance being the coarse superabrasive particles 10. In anotherembodiment, the mixture 8 may comprise ultra-dispersed diamond particles12 in an amount greater than zero weight percent and less than about 5weight percent, and more specifically in an amount greater than zeroweight percent to about 4 weight percent, with the balance being thecoarse superabrasive particles 10. In a more detailed embodiment, theultra-dispersed diamond particles 12 are present in the mixture 8 in anamount from about 0.1 weight percent to about 3 weight percent, and morespecifically in an amount from about 0.1 weight percent to about 2weight percent, with the balance being the coarse superabrasiveparticles 10. In another more detailed embodiment, the ultra-disperseddiamond particles 12 are present in the mixture 8 in an amount fromabout 0.1 weight percent to about 1.5 weight percent, and morespecifically in an amount from about 0.1 weight percent to about 1weight percent, with the balance being the coarse diamond particles 10.In yet a more specific detailed embodiment, the ultra-dispersed diamondparticles 12 are present in the mixture 8 in an amount from about 0.1weight percent to about 0.5 weight percent, and more specifically in anamount from about 0.1 weight percent to about 0.25 weight percent, withthe balance being the coarse superabrasive particles 10. In yet anothermore specific detailed embodiment, the ultra-dispersed diamond particles12 are present in the mixture 8 in an amount greater than zero weightpercent to about 0.1 weight percent with the balance being the coarsesuperabrasive particles 10.

In another more detailed embodiment, the coarse superabrasive particles10 of the mixture 8 may exhibit a bimodal or greater distribution ofparticle sizes. For example, the mixture 8 may include ultra-disperseddiamond particles 12 in an amount of about 0.1 weight percent to lessthan about 5 weight percent of the mixture 8 with the balance beingcoarse superabrasive particles 10. The formulation of the coarsesuperabrasive particles 10 may be about 75 weight percent to about 99weight percent diamond particles with an average size of about 10 μm toabout 40 μm and the balance being diamond particles exhibiting anaverage size of about 1 μm to about 10 μm. It should be understood thatany of the above ranges of various sizes and weight percentages for thecoarse superabrasive particles 10 and the ultra-dispersed diamondparticles 12 may be combined and processed according to any of themethods disclosed herein (i.e. time, temperature, and pressureparameters). As mentioned above, in one embodiment, superabrasiveparticles 10 may comprise diamond. In other embodiments, superabrasiveparticles 10 may comprise boron nitride, silicon carbide, etc., withoutlimitation.

Referring now to both FIGS. 1 and 2, the sintered superabrasive element2 will exhibit, to a substantial extent, the same or similargrain/particle size as the grain/particle size and relative weightpercentages of the precursor materials used (i.e., the coarsesuperabrasive particles 10 and ultra-dispersed diamond particles 12).Additionally, some carbon phases present in the ultra-dispersed diamondparticles 12 may be present in the final sintered superabrasive element2 in detectable small amounts. Such phases include small amounts ofamorphous carbon, carbon onion, or both that are not transformed todiamond or otherwise transformed during the HPHT sintering process.

In many applications, it may be desirable to form the superabrasiveelement 2 on a substrate. For example, in one embodiment, thesuperabrasive element 2 may comprise a PDC cutting element. FIG. 3 showsa schematic illustration of the process for forming any of thesuperabrasive elements 2 disclosed herein on a substrate to form a PDCcutting element. With reference to FIG. 3, the mixture 8 of the coarsesuperabrasive particles 10 and ultra-dispersed diamond particles 12 ispositioned adjacent to an interfacial surface 16 of a suitable substrate18. As shown in FIG. 3, in one embodiment, substrate 18 may be generallycylindrical. More generally, the substrate 18 may comprise any selectedshape and size, without limitation. Although FIG. 3 shows theinterfacial surface 16 as being substantially planar, the interfacialsurface 16 may exhibit a selected nonplanar topography, withoutlimitation. The substrate 18 may comprise, for example, cobalt-cementedtungsten carbide or another suitable material. Other materials that maybe used for the substrate 18 include, without limitation, cementedcarbides including titanium carbide, niobium carbide, tantalum carbide,vanadium carbide, iron, nickel, and combinations thereof. The mixture 8and the substrate 14 may be subjected to an HPHT sintering process toform a superabrasive table 13 (e.g., a PCD table) bonded to theinterfacial surface 16 of substrate 18 to form an element suitable foruse as a cutting element 15 (e.g., a PDC cutting element).

As previously discussed, a catalyst material (e.g., cobalt, nickel,iron, alloys of the foregoing, etc.) may be employed for promotingintergrowth between the coarse superabrasive particles 10, theultra-dispersed diamond particles 12, and/or intergrowth between thecoarse superabrasive particles grains 10 and the ultra-dispersed diamondparticles 12. For example, if superabrasive particles 10 comprisediamond, when the mixture 8 is placed adjacent to, for example, acobalt-cemented tungsten carbide substrate 18 and subjected to the HPHTsintering process, molten cobalt may wick or sweep into the mixture 8from the substrate 18. Such cobalt may remain in the superabrasive(e.g., PCD) table 13 upon sintering and cooling. One specific embodimentof a non-cobalt catalyst is the INVAR® alloy. In other embodiments, acatalyst may be provided prior to sintering, as a layer of materialbetween the substrate 18 and the mixture 8, within the mixture 8 as apowder, or as otherwise known in the art. Of course, when thesuperabrasive table 13 includes a catalyst material, the thermalstability may be lower compared to when the superabrasive table 13 isfabricated without the catalyst material. Moreover, such a catalystmaterial may be at least partially removed (e.g., by acid-leaching or asotherwise known in the art) from at least a portion of the superabrasivetable 13 to a selected depth from an exterior surface of thesuperabrasive table 13, if desired

Still, in other embodiments, the superabrasive table 13 may be sinteredand, subsequently, bonded to the substrate 18 by brazing, using an HPHTprocess, or any other suitable joining technique, without limitation.

FIGS. 4 and 5 show an isometric view and a top elevation view,respectively, of a rotary drill bit 20 in accordance with one embodimentof the present invention. The rotary drill bit 20 includes at least onesuperabrasive cutting element manufactured in accordance withembodiments of the present invention. The rotary drill bit 20 includes abit body 22 including radially and longitudinally extending blades 38with leading faces 40, and a threaded pin connection 50 for connectingthe bit body 22 to a drilling string. The bit body 22 defines a leadingend structure for drilling into a subterranean formation by rotationabout a longitudinal axis 36 and application of weight-on-bit. In oneembodiment, at least one superabrasive cutting element comprisingpolycrystalline diamond may be affixed to rotary drill bit 20. Forexample, as best shown in FIG. 5, a plurality of cutting elements 24 aresecured to the blades 38, each cutting element 24 including a PCD table28 bonded to a substrate 26. The PCD tables 28 and substrates 26 may befabricated and structured in accordance with any of the disclosedembodiments. More generally, the diamond tables 28 may comprise anysuperabrasive encompassed by the instant disclosure, without limitation.In addition, if desired, in some embodiments, some of the cuttingelements 24 may be conventional in construction, if desired. Also,circumferentially adjacent blades 38 define so-called junk slots 42therebetween, as known in the art. Additionally, the rotary drill bit 20includes a plurality of nozzle cavities 46 for communicating drillingfluid from the interior of the rotary drill bit 20 to the cuttingelements 24.

FIGS. 4 and 5 merely depict one embodiment of a rotary drill bit thatemploys at least one cutting element including a superabrasive elementfabricated and structured in accordance with the disclosed embodiments,without limitation. The drill bit 20 is used to represent any number ofearth-boring tools or drilling tools, including, for example, core bits,roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits,reamers, reamer wings, or any other downhole tool includingsuperabrasive cutting elements or inserts, without limitation.

The superabrasive elements disclosed herein may also be utilized inapplications other than cutting technology. The embodiments ofsuperabrasive elements disclosed herein may be used in wire dies,bearings, artificial joints, inserts, cutting elements, and heat sinks.Thus, any of the superabrasive elements formed by the methods disclosedherein may be employed for forming an article of manufacture includingat least one superabrasive element.

Thus, the embodiments of superabrasive elements disclosed herein may beused on any apparatus or structure in which at least one conventionalPCD element is typically used. In one embodiment, a rotor and a stator(i.e., a thrust bearing apparatus) may each include a superabrasiveelement according to any of the embodiments disclosed herein and may beoperably assembled to a downhole drilling assembly. U.S. Pat. Nos.4,410,054; 4,560,014; 5,364,192; 5,368,398; and 5,480,233, thedisclosure of each of which is incorporated herein, in its entirety, bythis reference, disclose subterranean drilling systems within whichbearing apparatuses utilizing PCD elements disclosed herein may beincorporated. The embodiments of superabrasive elements disclosed hereinmay also form all or part of heat sinks, wire dies, bearing elements,cutting elements, cutting inserts (e.g., on a roller cone type drillbit), machining inserts, or any other article of manufacture as known inthe art. Other examples of articles of manufacture that may use any ofPCD elements disclosed herein are disclosed in U.S. Pat. Nos. 4,811,801;4,274,900; 4,268,276; 4,468,138; 4,738,322; 4,913,247; 5,016,718;5,092,687; 5,120,327; 5,135,061; 5,154,245; 5,460,233; 5,544,713; and6,793,681, the disclosure of each of which is incorporated herein, inits entirety, by this reference.

The following working examples of the present invention set forthvarious formulations that have been used to form PDC cutting elements.The following working examples provide further detail in connection withthe specific embodiments described above.

Comparative Example 1

A conventional PDC was formed from a mixture of coarse diamond particlesbeing in excess of about 90 weight percent of the mixture with thebalance being relatively fine diamond particles. The coarse diamondparticles exhibit an average particle size about ten times the averageparticle size of the relatively fine diamond particles of the mixture.The mixture contained no ultra-dispersed diamond particles. The mixturewas placed adjacent to a cobalt-cemented tungsten carbide substrate. Themixture and substrate were placed in a niobium can and sintered at atemperature of about 1400° C. and about 69 kilobar for about 90 secondsto form the conventional PDC. The thermal stability of the as-formedconventional PDC was evaluated by measuring the distance cut in agranite workpiece prior to failure without using coolant. The distancecut is considered representative of the thermal stability of the PDC.The conventional PDC was able to cut a distance of only 1643 linear feetin the granite workpiece.

Example 2

A mixture was formed of about 0.1 weight percent ultra-dispersed diamondparticles with the balance comprising the same diamond formulation asexample 1. The mixture was placed adjacent to a cobalt-cemented tungstencarbide substrate. The mixture and substrate were placed within aniobium can and sintered at a temperature of about 1400° C. and about 69kilobar for about 90 seconds to form a PDC. The thermal stability of theas-formed PDC was evaluated by measuring the distance cut in a graniteworkpiece without using coolant. The PDC fabricated in example 2 wasable to cut a distance of 2135 linear feet in a granite workpiececompared to the distance of only 1643 linear feet cut by theconventional PDC of example 1. Thus, thermal stability tests indicatethat the PDC of example 2 exhibited a significantly improved thermalstability compared to the conventional PDC of comparative example 1.Wear flat volume tests indicated that there was no substantialdifference in wear resistance between the PDC of example 2 and theconventional PDC of comparative example 1.

Example 3

A mixture was formed of about 1 weight percent ultra-dispersed diamondparticles with the balance comprising the same diamond formulation asexample 1. The mixture was placed adjacent to a cobalt-cemented tungstencarbide substrate. The mixture and substrate were placed within aniobium can and sintered at a temperature of about 1400° C. and about 69kilobar for about 90 seconds to form a PDC. The PDC fabricated inexample 3 was able to cut a distance of 1868 linear feet in a graniteworkpiece compared to a distance of only 1643 linear feet cut by theconventional PDC of example 1. Thus, thermal stability tests indicatethat the PDC of example 3 also exhibited a significantly improvedthermal stability compared to the conventional PDC of example 1. Wearflat volume tests indicated that there was no substantial difference inwear resistance between the PDC of example 3 and the conventional PDC ofexample 1.

From the foregoing it will be appreciated that, although specificembodiments and working examples of the present invention have beendescribed herein for purposes of illustration, various modifications maybe made without deviating from the spirit and scope of the presentinvention. Accordingly, the present invention is not limited except asby the appended claims. The words “including” and “having,” as usedherein, including the claims, shall have the same meaning as the word“comprising.”

1. A method of fabricating a polycrystalline diamond element,comprising: mixing a plurality of sp²-carbon-containing particles and aplurality of diamond particles to form a mixture, wherein an amount ofthe plurality of sp²-carbon-containing particles present in the mixtureis effective to increase a thermal stability of the polycrystallinediamond element formed at least partially from the mixture; andsintering the mixture in the presence of a catalyst material to form thepolycrystalline diamond element.
 2. The method of claim 1 wherein atleast a portion of the plurality of sp²-carbon-containing particlescomprise a plurality of nanocrystalline diamond particles.
 3. The methodof claim 1 wherein at least a portion of the plurality ofsp²-carbon-containing particles comprise a plurality of ultra-disperseddiamond particles.
 4. The method of claim 1 wherein at least a portionof the plurality of sp²-carbon-containing particles comprise carbononion.
 5. The method of claim 1 wherein at least a portion of theplurality of sp²-carbon-containing particles comprise amorphous carbon.6. The method of claim 1, further comprising: disposing the mixtureadjacent a substrate including the catalyst material therein; andwherein sintering the mixture in the presence of a catalyst material toform the polycrystalline diamond element comprises infiltrating themixture with the catalyst material from the substrate.
 7. The method ofclaim 1, further comprising: disposing the mixture adjacent a substrateincluding the catalyst material therein; and wherein sintering themixture in the presence of a catalyst material to form thepolycrystalline diamond element comprises forming the polycrystallinediamond element as table on the substrate.
 8. The method of claim 7wherein the substrate comprises cemented tungsten carbide.
 9. The methodof claim 1 wherein the amount of the plurality of sp²-carbon-containingparticles is greater than zero to about 5 weight percent of the mixture.10. The method of claim 1 wherein the amount of the plurality ofsp²-carbon-containing particles is about 0.1 weight percent to about 0.5weight percent of the mixture.
 11. The method of claim 1 wherein theamount of the sp²-carbon-containing particles is greater than zeroweight percent to about 1 weight percent of the mixture.
 12. The methodof claim 1 wherein the amount of the plurality of sp²-carbon-containingparticles is greater than zero weight percent to about 2 weight percentof the mixture.
 13. The method of claim 1, further comprising removing aportion of the catalyst material from the polycrystalline diamondelement.
 14. The method of claim 13 wherein removing a portion of thecatalyst material from the polycrystalline diamond element comprisesleaching the catalyst material from the polycrystalline diamond element.15. The method of claim 1, further comprising bonding thepolycrystalline diamond element to a substrate.
 16. The method of claim1 wherein the catalyst material comprises cobalt, iron, nickel, oralloys thereof.
 17. A method of fabricating a polycrystalline diamondelement, comprising: mixing a plurality of nanocrystalline diamondparticles and a plurality of diamond particles to form a mixture,wherein an amount of the plurality of nanocrystalline diamond particlespresent in the mixture is effective to increase a thermal stability ofthe polycrystalline diamond element formed at least partially from themixture; and sintering the mixture in the presence of a catalystmaterial to form the polycrystalline diamond element.
 18. The method ofclaim 17 wherein the amount of the plurality of nanocrystalline diamondparticles is greater than zero to about 5 weight percent of the mixture.19. The method of claim 17 wherein the amount of the plurality ofnanocrystalline diamond particles is about 0.1 weight percent to about0.5 weight percent of the mixture.
 20. The method of claim 17 whereinthe amount of the plurality of nanocrystalline diamond particles isgreater than zero weight percent to about 1 weight percent of themixture.
 21. The method of claim 17 wherein the amount of the pluralityof nanocrystalline diamond particles is greater than zero weight percentto about 2 weight percent of the mixture.
 22. The method of claim 17wherein at least a portion of the plurality of nanocrystalline diamondparticles comprise a plurality of ultra-dispersed diamond particles. 23.The method of claim 17 wherein at least a portion of the plurality ofnanocrystalline diamond particles comprise a plurality ofsp²-carbon-containing particles.
 24. The method of claim 17, furthercomprising removing a portion of the catalyst material from thepolycrystalline diamond element.
 25. The method of claim 24 whereinremoving a portion of the catalyst material from the polycrystallinediamond element comprises leaching the catalyst material from thepolycrystalline diamond element.
 26. The method of claim 17, furthercomprising bonding the polycrystalline diamond element to a substrate.27. A method of fabricating a polycrystalline diamond element,comprising: mixing a plurality of sp²-carbon-containing particles and aplurality of diamond particles to form a mixture; and sintering themixture in the presence of a catalyst material to form thepolycrystalline diamond element, wherein the polycrystalline diamondelement is capable of cutting a distance of at least about 2135 linearfeet in a vertical turret lathe thermal stability test.
 28. A method offabricating a polycrystalline diamond compact, comprising: mixing aplurality of sp²-carbon-containing particles and a plurality of diamondparticles to form a mixture, wherein an amount of the plurality ofsp²-carbon-containing particles present in the mixture is effective toincrease a thermal stability of the polycrystalline diamond elementformed at least partially from the mixture; disposing the mixtureadjacent to a cemented carbide substrate; and subject the mixture andthe cemented carbide substrate to a high-pressure/high-temperatureprocess to sinter the mixture in the presence of a catalyst materialinfiltrated from the cemented carbide substrate to form thepolycrystalline diamond compact.